Widely-used chemotherapy drugs, such as platinum, exhibit a high level of treatment-associated toxicity including neurotoxicity which is often dose limiting and can be devastating to a patient's quality of life long after the therapy ends. We have identified that suppression of RhoA signaling by p160ROCK/Rho kinase inhibitor Y-27632, which inhibits cancer cell motility and invasion, can reverse anti-cancer drug-induced neurodegeneration in the novel cisplatin-induced peripheral neuropathy (CIPN) mouse model developed in this laboratory. Few molecular pathways demonstrate this unique capacity of inhibiting cancer cell expansion while exhibiting neuroprotective effects. Establishing the mechanisms underlying this pathway to increase cancer-attacking efficacy will have significant impact since both platinum and Y-27632 have proven to be clinically safe and can expand to many anti-cancer drug applications. In this R15 AREA project, we propose to use both normal and tumor-bearing mice to test the hypothesis that suppression of Rho GTPase signaling coupled with chemotherapy drugs provides an effective strategy for attacking cancer while protecting neurons. Specific aim 1 will investigate two potential molecular mechanisms (ERM protein activation and redistribution to actin to activate Fas receptor/CD95 and SRF-dependent gene transcription) by which suppression of Rho GTPase signaling pathway protects neurons from cisplatin-induced neurotoxicity. Specific aim 2 will apply innovative small molecule Rac1/Cdc42 activator/inhibitor reservoirs to investigate whether crosstalks among the subclasses of Rho GTPases enhance the RhoA suppression-mediated inhibition of CIPN. Specific aim 3 will investigate RhoA pathway inhibition and neuroprotection in cisplatin anti-cancer therapy in murine models of primary and metastatic lung carcinoma. We will determine whether cisplatin and Y-27632 (or RhoA/SRF-dependent transcription inhibitor CCG-1423) combinations enhance anti-cancer efficacy while reducing CIPN (measured by improving sural nerve conduction and touch sensation) in immunocompetent mice inoculated with syngeneic Lewis Lung carcinoma cells. These studies, engaging the continuous graduate and undergraduate student research in this laboratory, will establish Rho GTPase signaling as an innovative drug target for combined neuroprotection and cancer inhibition in clinical cancer therapy. PUBLIC HEALTH RELEVANCE: Widely-used chemotherapy drugs, such as platinum, exhibit a high level of treatment-associated toxicity including neurotoxicity which is often dose limiting and can be devastating to a patient's quality of life long after the therapy ends. This project is a preclinical study to determine whether suppression of Rho GTPase signaling coupled with chemotherapy drugs provides an effective strategy for attacking cancer while protecting neurons.